Automobile wheels come in two basic kinds: steel wheels and alloy wheels. Steel wheels are standard equipment for cars, because they are inexpensive. Unfortunately, steel wheel are utilitarian in appearance and use, and are often covered with hub caps to disguise their utilitarian appearance. Alloy wheels are usually not offered as standard equipment because they are expensive, so if car owners want to improve the appearance of their cars, they must buy alloy wheels from the car dealer or from after-market sellers. In addition to their functional use as wheels, alloy wheels dramatically improve the vehicle's appearance.
Despite their improvement of a vehicle's appearance, alloy wheels suffer from a couple of problems. First, alloy wheels typically have large open vents. The open vent designs allow for more intricate wheel styles, but they also allow unsightly brake mechanisms to be seen through the alloy wheel, including the brake drums, brake discs and overall braking mechanisms. Depending upon the vehicle, some use brake drums and others use disc brakes. Through daily use, braking mechanisms often have rust on their surfaces. This rust does not impair the vehicles ability to reduce speed, however, the rusty brake drums and discs are not attractive when seen through the open vents of an alloy wheel. Since consumers purchase alloy wheels mainly for their cosmetic looks, visibility of the unsightly rusty brake drums and discs defeats the purpose of the alloy wheels.
Second, braking mechanisms such as disc brakes create significant amounts of brake dust. Brake dust is corrosive and can damage the finish of an alloy wheel, which is both unsightly and damaging to alloy wheels if not washed away frequently. Although brake dust will cover both steel and alloy wheels, it is more of a problem with alloy wheels. Gradually over many years, the alloy wheel finish may become pitted or dull from the brake dust's corrosive nature. Since alloy wheels are expensive relative to steel wheels, consumers do not want brake dust damaging their alloy wheels. Additionally, the brake dust makes the alloy wheels look dirty. Through the course of daily driving, a vehicle and its wheels will become dirty from the dirt and grime found on roads. However, the brake dust significantly exacerbates the appearance of dirt on the alloy wheel.